This invention relates to demagnetizing apparatus for electromagnets and workpieces held thereby and more particularly to such apparatus effecting periodically reversing energizations of decreasing amplitude.
In many environments in which an electromagnet is used for holding a workpiece, it is necessary to provide some means for demagnetizing the electromagnet and a workpiece held thereby before the workpiece can be readily removed from the holding magnet. Otherwise, the residual magnetism left in both the magnet and the workpiece may be sufficient to inhibit easy removal of the workpiece from the magnet. One example of such a situation is where an electromatic chuck is used for holding one or a plurality of workpieces for a grinding operation.
While various automatic demagnetizing systems have been devised and sold previously, such systems have typically been relatively complex and expensive and have encountered certain problems in employing modern triggerable semi-conductor switching devices such as SCR's and triacs.
Among the several objects of the present invention may be noted the provision of apparatus for automatically deenergizing a workpiece-holding electromagnet, the provision of such apparatus which employs triggerable, semi-conductor switching devices, the provision of such apparatus which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.